I first joined toodledo in 2009. Someone from toodledo promised in the forums that completion date editing was in the pipeline for release in the near future so I decided to join and pay for the pro version to support development costs. More than two years later, I'm still waiting for this "feature." I too normally review my tasks in the morning, which means that checking off tasks for the previous day results in them displaying as if I'd completed them late. I hate this so much that often I end up deleting tasks after completing them instead of checking them off, and I don't get satisfaction of seeing them marked complete. Sometimes I even switch the due date first to the current day and then mark them complete even if they've been completed for days. It's quite absurd.
Despite this, toodledo still meets my needs better than any other tool (especially because of the sorting flexibility, wealth of fields, online task storage and multiplatform availability, and ssl), but I do check out alternatives periodically hoping to jump on the opportunity to switch. I guess it's time for my periodic checking to see if I can find another tool that works for me and allows me to mark when a task was completed.
I would be happy even if this option was only available on the website and not in the APIs or apps at first. It's not a difficult change.

It's bizarre that your API allows the Completion Date to be changed but you, as the website developer, cannot figure out a way to accommodate those users who have been asking for years to have this feature.

Are you simply refusing to do it because it would interfere with your 1-week limit of viewing completed tasks for free subscriptions?

I too need this feature and won't upgrade to a pro version unless this can be made to work. For instance, I need project tracking for my people and other than this one feature everything seems to fit our needs. However, not being able to enter the actual completion date makes the data useless.

From a management point of view, one of the suggestions of having a checkoff date and a completion date would be very useful as well.

Also, it appears that lacking this feature makes the goal chain tool useless as well, as not getting the task checked on the correct day seems to break the chain. Perhaps there is a way to fix this behavior?

Anyway for us, the value of the pro account is in the data, history, progress, tracking etc. So without the ability to enter correct completion dates (times to, as a matter of fact), the tool is of limited utility.

One comment was that third party apps could be used to add this feature. Clunky, but perhaps workable. Can anyone explain how that works?

I also would like to have the ability to change completion dates. You say it's not a high priority, but many users have been asking for it for years. Why hasn't it ascended to the top of the list? How can we make it a priority?

Here's another vote to for the ability to change the completion date. I often do not mark tasks completed on the actual date when I completed them. But I would like to keep such a record. I understand that for legal reasons there may be a need to record the date when the actual checkoff was done, in a non-editable field.

Please, please....I need this too. The fact that I have to sit down at my computer at 11:30pm every night just to check tasks off on the proper date is ludicrous, but whenever I fail to do so, it corrupts the statistics and the goal chains.

There's a suggestion above saying that one of the third-party apps may be able to do this. Does anyone know of one? If I had to, I'd buy an additional app just to check things off of my lists the following morning.

Or any other workarounds? I've tried csv export-import, but Toodledo ignores the "Completed" field when re-importing, which is also not cool.